Editorial

San Onofre's cloudy future

Can the damaged nuclear power plant be repaired and restarted? And if so, what then?

The San Onofre nuclear plant, just south of Orange County, is shown. Both… (Los Angeles Times )

These are dark days at the San Onofre nuclear plant just south of Orange County. Both of its reactors have been shut down for more than four months, when abnormal "thinning" was discovered in the tubes of recently installed steam generators. Neither reactor will come back on line this summer, and after that, it's still unclear whether one or both will be switched on again and if so, at full power or partial — or whether they'll stay shut for the foreseeable future.

On Monday, the Nuclear Regulatory Commission provided a troubling assessment of the situation at San Onofre. A flaw in the design of the new generators — which cost ratepayers $671 million to build — appears to be responsible for making their tightly bundled tubes vibrate too much and rub together. The result is an alarming level of wear in equipment that is still in its relative infancy, especially in Unit 3, where, according to NRC officials, the damage reaches a level far beyond what's been seen before in this nation's nuclear industry. The rupture of one or more tubes could release radiation.

Southern California Edison, the majority owner of the plant, has suggested that running less-damaged Unit 2 at lower power might reduce or eliminate the vibration. That could be worth trying, but only with stringent, on-site monitoring by NRC inspectors.

But the NRC also refuses to rule out the possibility that the two generators will need to be replaced altogether. And who would pay for that? The maker of the generators, Mitsubishi Heavy Industries, is largely responsible for what the NRC believes to be faulty computer modeling, but Mitsubishi's liability under its agreement with Edison is limited to a fraction of the replacement cost. Considering that these are aging reactors that have gone through about 75% of their licensed operating time, spending the money to replace the generators again would be a questionable move at best; certainly, ratepayers shouldn't be on the hook for the additional costs.

As the NRC continues its probe of San Onofre, among the issues it will examine is whether Edison officials accurately characterized the new steam generators, which were installed in 2010 and 2011, when they said they were nearly identical to the old ones. That set the stage for a streamlined approval process. Now it appears that the design might not have been so similar after all. Hundreds more tubes were added in Unit 3, and the shape of the support structure for those tubes also was redesigned. The modified structure was intended to improve performance, but any significant change calls for stringent regulatory oversight. The NRC also should be examining its own actions in this regard; Edison shared the design changes with the nuclear agency, which should bear responsibility if it failed to insist on the proper level of scrutiny.

As long as the region doesn't suffer an extreme heat wave this summer, Edison's customers should be able to get through the season of peak demand without rolling blackouts, thanks to an energy conservation program plus power from two retired natural gas generators in Huntington Beach that were temporarily brought back to life. Things might get uncomfortably warm at times, but the millions of people who live within a 50-mile radius of San Onofre are relying on the NRC to forbid any restart without a full understanding of exactly how the vibration originated and full confidence that even partial operations can be undertaken safely.

The decision about whether to start up the reactors is essentially an engineering issue. But the bigger policy question for both Edison and regulators is the long-term future of the aging plant. San Onofre's two current reactors have been operating since 1983 and '84, respectively; the license for both expires in 2022. (Unit 1 was retired in 1992.) Edison says it has not yet determined whether to seek a 20-year license extension, a process that it would have to begin in 2017 to be completed in time.

It should not. Instead of spending the next five years figuring out how to keep the plant going indefinitely, Edison should be using that time to develop other ways to generate the needed power, especially from reliable, sustainable sources such as solar and wind.